Coaxial line stretchers or small wire filaments are conventionally used to tune the phase in a radio frequency (“RF”) sub-assembly such as an individual transmission line of an apparatus such as RF power combiner or RF divider. For example, a power combiner, divider, or boresight RF distribution network may consist of multiple interconnected transmission line sub-assemblies that each has a RF signal phase error. The combined RF signal phase error of the interconnected sub-assemblies may result in an overall phase error that exceeds the allowable phase tolerance for the system, therefore requiring phase tuning of the individual sub-assemblies. However, adjustable coaxial line stretchers (“trombone” line stretchers) are expensive, require a relatively large amount of space, are non-hermetic, and can be tricky to adjust. Phase tuning operations using wire filaments is a labor intensive process that requires opening a RF cavity (where present), and then soldering and trimming of a thin wire to achieve phase adjustment. If not performed correctly the first time, this soldering and trimming process must be repeated.